1. Field of the Invention
The present invention relates to a method for data copy between a DB system, which is usually operated in a computer system, in particular, a computer system operating a database (hereinafter referred to as “DB system”), (hereinafter referred to as “currently used system”) and a computer system, in which data of the currently used system is copied and used, (hereinafter referred to as “standby system”), and a method for data recovery in the standby system.
2. Description of the Related Art
In a DB system in which a database (hereinafter also referred to as “DB”) is established and the DB is operated, as a method of taking backup of data constituting the DB (hereinafter referred to as “DB data”), there is a technique for preparing a DB system, which has the same structure as a currently used system, as a standby system and copying DB data of the currently used system to the standby system.
If the above-mentioned method is used, when the currently used system stops operation due to some reason, availability of the entire system is improved by causing the standby system to operate. In addition, by setting the currently used system and the standby system in physically remote places, respectively, even if a natural disaster such as an earthquake has occurred in the place where the currently used system is set, it becomes possible to recover the DB data in the standby system. A system having such currently used and standby systems will be hereinafter referred to as disaster recovery (DR) system.
In the DR system, data transfer between the currently used system and the standby system may be performed between storage apparatuses storing the DB data. Such data transfer between the storage apparatuses will be hereinafter referred to as remote copy.
As a method for the remote copy, there are two kinds, namely, synchronous remote copy and asynchronous remote copy. In the synchronous remote copy, since update of the DB data is synchronized between the storage apparatus of the currently used system and the storage apparatus of the standby system (identity of contents of the DB data is guaranteed), reliability of the data transferred to the standby system is high. On the other hand, in order to synchronize the DB data, the currently used system is required to wait for a report on completion of processing while the DB data is being transferred to the standby system, and performance of the currently used system declines.
On the other hand, in the asynchronous remote copy, since data is transferred without synchronizing the DB data between the storage apparatus of the currently used system and the storage apparatus of the standby system, contrary to the synchronous remote copy, although performance of the currently used system does not decline much, reliability (or recency) of the data transferred to the standby system declines.
JP-A-2003-6016 discloses a method of giving priorities to each of logical volume groups and executing asynchronous remote copy in accordance with the priorities between storage apparatuses of a currently used system and a standby system. In addition, as an example of the method, the laid-open patent application discloses that a priority of a logical volume, in which a log of a DB is stored, is set high, and the log is transferred to the storage apparatus of the standby system preferentially compared with other DB data.